In the spring of 1965, within weeks of 3,500 American Marines arriving in Vietnam, a 39-year-old Briton named Larry Burrows began work on a feature for LIFE magazine, chronicling the day-to-day experience of U.S. troops on the ground – and in the air – in the midst of the rapidly widening war. The photographs in this gallery focus on a calamitous March 31, 1965, helicopter mission; Burrows’ “report from Da Nang”, featuring his pictures and his personal account of the harrowing operation, was published two weeks later as a now-famous cover story in the April 16, 1965, issue of LIFE.

Photo: Man your battle stations: The crew chief of helicopter Yankee Papa 13, lance corporal James C. Farley, mans an M-60 machine gun during a mission near Da Nang, Vietnam on March 31, 1965. (Photo by Larry Burrows/Time & Life Pictures)

Pedestrians cover their face as they walk along the dusty road in Kathmandu, Nepal February 27, 2017. Nepal has forced 2,500 old vehicles off roads in its capital city of Kathmandu, part of a fight against alarming air pollution levels that have hit nine times World Health Organisation (WHO) limits. Air pollution has been a chronic problem in rapidly growing Kathmandu, which sits in a Himalayan valley and is home to more than 3mn people. (Photo by Navesh Chitrakar/Reuters)

Garbage pickers collect ride on donkey cart while looking for recyclable materials at a rubbish dump in the outskirts of Baghdad, Iraq, August 23, 2016. Despite its huge untapped oil and gas reserves and steadily rising oil output and revenue, 23 percent of the population live below the poverty line, according to the Ministry of Planning. (Photo by Khalid al Mousily/Reuters)

A member of Four Paws International team carries a pelican to be taken out of Gaza, at a zoo in Khan Younis in the southern Gaza Strip August 23, 2016. Fifteen animals including a bengal tiger were removed from “the world’s worst zoo” in the Gaza town of Khan Younis as it was finally closed down. Animal welfare group, Four Paws International, will help bring most of the refugees to a zoo in Jordan, but the tiger will be taken to a refuge in South Africa. (Photo by Ibraheem Abu Mustafa/Reuters)

In Mumbai, the windows of new high-rise apartment blocks, old low-rise residential buildings and shantytown shacks portray the disparity in living conditions and incomes in the Indian city. Rents for a place to live range from more than $2,000 to less than $5 a month. Here: Windows and doors of an old residential building are pictured in central Mumbai October 10, 2014. The cost for buying a residential apartment in Mumbai close to the city centre ranges from 12,000 Indian rupees ($ 200) per square feet to 112,552 Indian rupees ($ 1800) per square feet. (Photo by Danish Siddiqui/Reuters)

“Serengeti National Park encompasses 5,700 square miles of grassy plains and woodlands near the northern border of Tanzania, and is home to more than 3,500 lions grouped into a couple dozen prides. Photographer Nick Nichols and videographer Nathan Williamson made several extended trips to the Serengeti between July 2011 and January 2013, determined to break new visual ground in their coverage of the Serengeti Lions”. Photo: Cubs of the Simba East pride: too young to kill but old enough to crave meat. Adult females, and sometimes males, do the hunting. Zebras and wildebeests rank high as chosen prey in the rainy season. (Photo by Michael Nichols/National Geographic via The Atlantic)

A visitor takes a photograph from the North Star observation capsule onboard the cruise ship Quantum of the Seas which is currently docked at Southampton on October 31, 2014 in Southampton, England. Billed as the world's first smartship, Royal Caribbean's Quantum of the Seas is claimed to be the most high-tech cruise ship in the world, with high tech modifications such as virtual balconies in windowless rooms and features such as the first dodgem ride on water, and a skydiving simulator. The ship will shortly begin its voyage from Southampton, where it docked earlier this week, to New York before relocating to the Caribbean for the 2014-15 season. (Photo by Matt Cardy/Getty Images)

A prisoner from the Pedrinhas prison is carried to receive medical help after he was injured during a fight between rival gangs inside the jail, in Sao Luiz, capital of Maranhao state, January 8, 2014. The recent posting on a major Brazilian news website of a video filmed last December 17 by Pedrinhas prisoners of the decapitated and tortured bodies of rival inmates inside the jail has highlighted some of the problems present in the country's prison system which houses nearly twice as many prisoners as its capacity, according to official statistics. (Photo by Douglas Cunha/Reuters/O Estado do Maranhão)